Utilization of disposable test strip devices represents the most simple, fast and convenient technique for determination of a variety of analytes in body liquid samples, such as blood, plasma, serum, urine and saliva. For detecting analytes in body liquid samples by disposable test strips two major approaches are generally utilized. The first approach is immunochemical; antibody-antigen interaction based test strips comprise, in addition to an actual detection zone, also a control zone Immune assay based tests are historically rendered for hormone detection from blood or urine; manufacturing thereof is rather expensive, so as the final product, correspondingly.
The second major approach originates from enzymatic assays for colorimetric detection, wherein the presence of analyte in biological sample is determined qualitatively and/or semi-quantitavely by observing color changes within a detection portion of a test strip. Disposable analytic test strip devices for determination of analyte, such as ethanol, in human body liquid samples, such as whole blood, serum, saliva or urine, by means of colorimetric, alcohol oxidase based reaction are disclosed in U.S. Pat. No. 4,734,360 (Philips), U.S. Pat. No. 4,786,596 (Adams) and U.S. Pat. No. 4,810,633 (Bauer and Magers). Those test strip devices generally comprise the enzymes alcohol oxidase and peroxidase, along with a chromogenic indicator system incorporated into a carrier matrix. Alcohol oxidase functions as a catalyst to convert ethanol present along with ambient oxygen in a liquid sample to acetaldehyde and hydrogen peroxide. Peroxidase, in turn, functions as a catalyst to induce a color change in the hydrogen donor and convert the hydrogen peroxide to water. Determination of analyte levels in the sample is performed by visual estimation of shade and intensity of color developed in the detection area. Visual estimation can be performed qualitatively by observing color development in an otherwise blank detection area, as disclosed in e.g. U.S. Pat. No. 4,734,360, or semi-quantitavely, by visually comparing a tone and an intensity of the colored detection area to a printed standard/color map, as disclosed in U.S. Pat. No. 4,962,025 (Moldowan), for example. In opposite to immunochemical test strips, aforementioned enzymatic colorimetric solutions are not provided with a separate control area, whose purpose is to confirm that the test had worked correctly. Therefore, a common drawback of such tests is their rather low reliability, resulting in a high number of fault results. Disposable test strip devices comprising a distinct control area are also known. Thus, European patent No. 1,130,395 (Albarella et al) discloses a colorimetric test strip for detecting the absence or presence of glucose in urine, which test strip comprises, in addition to detection (“reagent”) areas, one or more reference color areas with predetermined color shades that are different from the color shades of said reagent areas prior to use. Said reference color areas are originally manufactured to comprise a predetermined color, so that the purpose thereof is to facilitate the comparison between the detection- and the reference zones. Mentioned reference color area(s) does not involve any reactive chemistry.
A test strip device, disclosed in European patent No. 1,621,887 (Matzinger et al), comprises a matrix having sample detection- and a control zones, provided with a first—and a second reagent composition, respectively. The test strip is, however, rendered for detection of glucose in blood samples and requires a measuring device, such as a reflectometer, for reading test results.
Mentioned prior art devices and related methods for detection of an analyte compound, such as alcohol, in a biological sample, are therefore hindered with several drawbacks, such as lack of reliability caused by the absence of an opportunity to perform control reaction and, therefore, increased possibility of obtaining fault results and/or misinterpretation of the results obtained. From the other hand, those test strip devices, that in one way or another are provided with the control zone, are typically rendered to detect other analytes than alcohol from such biological samples, whose collection is rather problematic, provided as impossibility therefor to be collected “on-the-go” and/or requirements for performing invasive actions.
Amidst body liquid samples collectable in a non-invasive manner saliva combines the advantages of sufficient sample quantity readily available, easy test performance and good approximation of analyte content, such as blood alcohol content (BAC), for example. Alcohol detection using a saliva sample has been proven to be a sensitive and accurate method; the relationship of saliva alcohol content and blood alcohol content has been shown to be almost 1:1. Furthermore, in comparison to gas sensor-based devices for detecting alcohol in exhaled breath and typically comprising an electronic reader, detection of alcohol in a liquid sample, such as saliva, by means of a disposable test strip may sometimes offer a more convenient, simple and effective solution for a mass customer. It is therefore desirable to combine detection simplicity and cost-effectiveness of colorimetric strips with high reliability, provided by immunochemical solutions, wherein high level of reliability is attained by exerting an additional control reaction, in one disposable test strip for detection of particular analytes, preferably alcohol, in saliva.